The present embodiment relates generally to a retarder for delaying setting of a cementing composition in a subterranean zone penetrated by a well bore.
In the drilling and completion of an oil or gas well, a cementing composition is often introduced in the well bore for cementing pipe strings. In this process, known as xe2x80x9cprimary cementing,xe2x80x9d a cementing composition is pumped into the annular space between the walls of the well bore and the pipe string. The cementing composition sets in the annular space, supporting and positioning the pipe string, and forming a substantially impermeable barrier which divides the well bore into subterranean zones. After primary cementing, the undesirable migration of fluids between zones is prevented. Likewise, cementing compositions are often subsequently introduced into a subterranean zone for remedial operations to recover circulation or to plug the well bore.
Regardless of the motivation for introducing the cementing composition into a subterranean zone (xe2x80x9ccementing operationsxe2x80x9d), with relatively hot or deep well bores it is often necessary to add a component, known as a xe2x80x9cretarder,xe2x80x9d to the cementing composition to slow setting, thereby increasing pumping time. A variety of factors affect the effectiveness of a retarder, including settling tendencies, environmental friendliness, and temperature range. For example, retarders are usually considered as those suitable for use at 100-200xc2x0 F. and retarders suitable for use at 200-300xc2x0 F. These temperatures are based on downhole temperature measured while circulating fluid in the well bore, known as the bottomhole circulating temperature (xe2x80x9cBHCTxe2x80x9d).
The present embodiment provides for the use of whey protein as a retarder in a cementing composition for use in cementing operations in a subterranean zone penetrated by a well bore.
Whey is readily available as a by-product from the dairy industry, and contains lactose, some salts, and a variety of proteins, including bovine serum albumin xe2x80x9cBSAxe2x80x9d (molecular weight 66,000 Daltons), alpha-lactoglobulin (molecular weight 14,000 Daltons), and beta-lactoglobulin (molecular weight 16,000 Daltons). The proteins may be isolated from the whey, the isolated proteins being generally referred to as xe2x80x9cwhey protein.xe2x80x9d Whey protein is readily available from Borculo Whey Products, Borculo, Netherlands, under the trademark xe2x80x9cPROXIME(trademark).xe2x80x9d Whey protein has designated whey protein concentrations (xe2x80x9cWPCxe2x80x9d) which vary from 10%-99%, and varying percentages of whey protein isolation (xe2x80x9cWPIxe2x80x9d) to indicate purity. The isoelectric point occurs at a pH of 5.4 approximately, and whey protein is water-soluble at all temperatures.
A cementing composition according to the present embodiment basically comprises a slurry including whey protein as a retarder, a cementitious material (xe2x80x9ccementxe2x80x9d), and sufficient water to form the slurry.
In one embodiment, the whey protein is used as a retarder in the cementing composition.
In an alternative embodiment, the whey protein is denatured by conventional denaturants, such as urea or sodium dodecyl sulfate (xe2x80x9cSDSxe2x80x9d), and then treated with formaldehyde or another crosslinker, and then with tartaric acid, to form modified whey protein. The modified whey protein is then used as a retarder in the cementing composition.
The cement may be Portland cement API Classes A-H (and preferably API Class G cement), or may alternatively be slag cement, pozzolana cement, gypsum cement, high alumina content cement, or high alkalinity cement. The desired amount of cement is understandably dependent on the cementing operation.
As will be understood by those skilled in the art, the amount of whey protein retarder included in the cementing composition can vary depending upon the temperature and the particular pumping time required for the cementing operation. Generally, the whey protein retarder of either of the above embodiments is present in the cementing composition in an amount in the range of 0.1% to 4.0% by weight of the cement in the composition.
The water used to form the cementing composition slurry can be fresh water or salt water. The water is preferably included in the cementing composition in an amount in the range of 30% to 60% by weight of the cement.
As is readily comprehended by those skilled in the art, the cementing composition may contain additional components (xe2x80x9cadditivesxe2x80x9d) to achieve desired properties. For example, the cementing composition may contain fine silica flour available from Halliburton Energy Services of Duncan, Okla., under the trademark xe2x80x9cSSA-1(trademark),xe2x80x9d fluid loss additives available from Halliburton Energy Services of Duncan, Okla., under the trademark xe2x80x9cHALAD(copyright)-600LE+,xe2x80x9d weighting additives available from Halliburton Energy Services of Duncan, Okla., under the trademark xe2x80x9cMICROMAX(trademark),xe2x80x9d and bond improving/expanding additives available from Halliburton Energy Services of Duncan, Okla., under the trademark xe2x80x9cMICROBOND HT(trademark).xe2x80x9d